NAME

SYNOPSIS

DESCRIPTION

[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
the ISO C standard.

The fputc() function shall write the byte specified by c (converted to an unsigned char) to the output
stream pointed to by stream, at the position indicated by the associated file-position indicator for the stream (if
defined), and shall advance the indicator appropriately. If the file cannot support positioning requests, or if the stream was
opened with append mode, the byte shall be appended to the output stream.

[CX] The
st_ctime and st_mtime fields of the file shall be marked for update between the successful execution of
fputc() and the next successful completion of a call to fflush() or fclose() on the same stream or a call to exit()
or abort().

RETURN VALUE

Upon successful completion, fputc() shall return the value it has written. Otherwise, it shall return EOF, the error
indicator for the stream shall be set, [CX] and errno shall be set to indicate the error.

ERRORS

The fputc() function shall fail if either the stream is unbuffered or the stream's buffer needs to be
flushed, and:

[EAGAIN]

[CX]
The O_NONBLOCK flag is set for the file descriptor underlying stream and the thread would be delayed in the write operation.

[EBADF]

[CX]
The file descriptor underlying stream is not a valid file descriptor open for writing.

[EFBIG]

[CX] An
attempt was made to write to a file that exceeds the maximum file size.

[EFBIG]

[XSI]
An attempt was made to write to a file that exceeds the process' file size limit.

[EFBIG]

[CX]
The file is a regular file and an attempt was made to write at or beyond the offset maximum.

[EINTR]

[CX]
The write operation was terminated due to the receipt of a signal, and no data was transferred.

[EIO]

[CX] A
physical I/O error has occurred, or the process is a member of a background process group attempting to write to its controlling
terminal, TOSTOP is set, the process is neither ignoring nor blocking SIGTTOU, and the process group of the process is orphaned.
This error may also be returned under implementation-defined conditions.

[ENOSPC]

[CX]
There was no free space remaining on the device containing the file.

[EPIPE]

[CX] An
attempt is made to write to a pipe or FIFO that is not open for reading by any process. A SIGPIPE signal shall also be sent to the
thread.